1. Field of the Invention
This invention relates to a laser applying apparatus, for example, a laser applying apparatus for ophthalmic operation using YAG laser light to treat a patient's eye to be examined.
2. Related Background Art
When carrying out an ophthalmic operation by the use of a YAG laser apparatus, a laser light of minimum output level which can provide a treatment effect must be applied to an eye to be examined in order to suppress the eye pressure of the eye to be examined from rising by the application of the laser light.
Also, the above-mentioned minimum output level which can provide a treatment effect differs greatly depending on the region of the eye to be examined and the substance of the treatment, and for example, several millijoules is required for the destruction of the front or rear pouch and several tens of millijoules is required for the excision of the iris. Therefore, in the conventional YAG laser apparatus for medical treatment, the output value of laser light output from a YAG laser source is fixed at a predetermined value equal to or greater than a maximum output level used during the treatment of the eye to be examined, and by changing the attenuation rate by the use of an attenuator, the output level of the laser light is adjusted to a minimum value which can provide a treatment effect.
YAG laser light has its refractive index distribution varied in conformity with the temperature distribution in the cross-section of a YAG rod, and the output of the laser light fluctuates as the resonance mode deviates. In a working machine or the like, the YA rod is water-cooled to thereby keep it at a constant temperature, whereby the deviation of the resonance mode and the fluctuation of the output of the laser light are prevented. However, the eye to be examined constantly vibrates about the fixation point, and in the YAG laser apparatus for medical treatment, it is necessary to follow the movement of the eye to be examined and always effect fine adjustment of the applied position of the laser light. Therefore, the water-cooling means for stabilizing the output as described above is difficult to adopt and it is usual with the conventional apparatus that air-cooling means is used for the YAG rod, and this leads to the problem that the intensity of the output of the laser light becomes unstable due to heat generation.
Also, as described above, in the conventional apparatus, laser light of maximum output level used is always produced and the output of the laser light is suitably attenuated by an attenuator, whereafter the laser light is applied to the eye to be examined and therefore, the energy efficiency is low and unnecessary heat is generated in the YAG laser source, and this also leads to the disadvantage that the intensity of the output of the laser light becomes more unstable.